Direction finding receiver



. J1me 1942- H. BERTHOLD 2, 8

DIRECTION FINDING mcmvmn Filed Nov. 9, 1939 Patented June 2, 1942 z esssi DIRECTION FINDING RECEIVER Hans Berthold, Berlin, Germany, assignor to C. Lorenz. Akticngesellschaft, Berlin-Tempelhof, Germany, av company Application November 9, 1939, Serial No. 303,513 In Germany November 9, 1938 4 Claims.

In order to obtain in direction finding systems of the rotatable frame or goniometer type a cardioid-shaped radiation diagram for the so called side determination, that is, the determination of the direction within the course line, it is in most cases necessary to employ a non-directional auxiliary antenna which is considerably higher than the finder means proper, this being a frame, for instance. Such expedient, however, is in general undesirable in View of space conditions. It is much better to restrict the height of the auxiliary antenna and aperiodically to amplify the efiect thereof. In such case, in the anode circuit of the amplifying tube a current is obtained which is in phase quadrature to the current in the antenna circuit. This dephased current if flowing through the finder coil will act directly to produce a cardioid diagram. The finding operation, however, also requires the current of the auxiliary antenna to be of the same phase condition as the current that flows in the antenna circuit itself, the object being to sharpen the minimum. However, phase displacement or using an auxiliary antenna amplifier arranged to provide for the said phase condition would entail very great voltage losses.

In accordance with the invention the auxiliary antenna amplifier is employed for the side determination only while the current intended for the sharpening effect is taken directly from the auxiliary antenna, this current being allowed to be considerably less than the current needed for the side determination. To such end a switching device is arranged to operate under the control of the direction finding switch and to connect the auxiliary antenna directly with the input circuit of the receiver, whereas in the case of sidedetermination the auxiliary antenna amplifier is by the same switching device connected between the two. In the simplest case the said switching device, which forms part of the auxiliary antenna amplifier, is connected with the direction finding switch by mechanic means, or a relay included in The invention will be understood from the following description, reference being had to the accompanying drawing in which Fig. 1 is a diagram showing the input circuit of a direction finding receiver of known type, Fig. 2 is a diagram representing one embodiment of the invention, this embodimentbeing of the kind in which the auxiliary antenna amplifier is arranged as an additional equipment while the said switching-over is efiected with the aid of a relay.

The receiver is designated P. A frame antenna R is connected to the input circuit K2 of the first electron tube by a coupling coil KI. In the arrangement shown in Fig. 1 the non directional auxiliary antenna H is coupled to circuit K2 by the direction finding switch PS and a coil K3. With the switch PS in position I the antenna H serves to sharpen the minimum during the finding operation. With the switch PS in positions 2, 3 antenna H is for the purpose of side determination combined with antenna R in a manner to afford either phase coincidence or phase opposition. Resistances RI, R2 here serve to.

establish phase quadrature.

In the arrangement represented in Fig. 2 the auxiliary antenna amplifier is constructed as an additional equipment HV. Antenna R is connected to receiver P in the same manner as shown in Fig. 1, whereas antenna H is joined to the input circuit of the equipment HV. This equipment comprises a relay S which is included in the anode circuit of an amplifying tube V and has two contacts SI, S2. The output circuit of equipment HV is connected to the same terminals of receiver P as is the case in Fig. 1. With the direction finding switch PS in position I, this being the position of course line finding, relay S is deenergized because the direct current circuit is open at condenser C. Antenna H is now in direct connection with receiver P. By turning the switch PS into position 2 or 3 the coil K3 will be connected in parallel with the tube V while relay S will be energized by the current that flows through this coil. The contacts SI, S2 hence break the direct connection of antenna H with receiver P and connect the tube V between the two. Accordingly, when restoring the switch PS into position I the equipment HV is disconnected thereby while antenna H is directly joined to receiver P.

The equipment HV may be used with any kind of direction finding receivers. When so used the phase resistances RI, R2, are no longer needed. The phase quadrature is effected by the amplifier.

Relay S is protected from the influence of high frequency currents.

Furthermore, in the case of long cables between the antenna system and receiver the equipment HV may be adjacent to the antenna system. In this way energy losses caused by the cables can be reduced, the anode circuit of the amplifier being considerably more low-ohmic than is antenna H itself.

What is claimed is:

l. A direction finding receiver comprising a radio receiver, a lei-directional antenna and an auxiliary non-directional antenna for this receiver, an aperiodic amplifier for such auxiliary antenna, a change over switch movable into different positions for connection of said auxiliary antenna corresponding to null finding and sensing operations, switching means for interconnecting said auxiliary antenna and receiver directly responsive to the setting of said switch into a position corresponding to null finding, and means for connecting said amplifier between said auxiliary antenna and receiver responsive to the setting of said switch into a position corresponding to sensing.

2. An arrangement according to claim 1, in which the said amplifier is an additional equipment adapted to be connected with the said auxiliary antenna and radio receiver.

3. An arrangement according to claim 1, wherein said amplifier comprises an amplifying tube and wherein said switching means and means for connecting comprise a relay, said tube having an anode circuit in which said relay is included, and connections for causing energization of said relay in response to the setting of said switch into a position corresponding to sensing.

4. An arrangement as defined in claim 1, in which the said switching .means and means for connecting comprise a relay associated with said amplifier and connections for controlling such relay from said changeover switch.

HANS BERTHOLD. 

